R is for... Rassilon

The founder of Time Lord society. A scientist, engineer and later politician, it was he who had harnessed the nucleus of a Black Hole to provide the power source for Gallifrey's initial experiments in time travel. This Black Hole had been the result of an artificially created supernova - detonated by fellow engineer Omega. He had apparently perished in the process, and it was Rassilon who would become known as the first and greatest of the Time Lords - the premier Lord President of the High Council.

He invented a number of objects which would bear his name - some ceremonial and some practical. These included items used in the inaugurations of future Presidents, such as the Sash and Coronet. The President also bore a sceptre-like device known as the Great Key, but the real key was actually the controlling mechanism for a powerful weapon and it was entrusted to the Chancellor.

The Sash was actually designed as a protection against the energies of the captured Black Hole nucleus, whist the Coronet gave its wearer the power to control the minds of others.

In its earliest days, Gallifrey was an interventionist power. Rassilon led campaigns against a race of giant vampires, devising Bow Ships as a weapon against them, and the spider-like Racnoss.

Whilst he went on to become a much loved, almost legendary figure, there were rumours that he abused his power. Another of his creations was the Time Scoop, and this was used to abduct alien beings to fight barbaric games, held in a region known as the Death Zone. He would come to be buried in the Dark Tower at the centre of this region - and it was even said that the other Time Lords had actually deposed him because of his tyranny and imprisoned him there.

Whilst Rassilon had died physically, his life force persisted. On his body was his ring, which it was claimed could bestow upon its wearer immortality. 

Future President Borusa discovered the Time Scoop and - wishing to become President Eternal - used it to hijack various incarnations of the Doctor to clear a path to the Dark Tower for him. 

An image of Rassilon appeared above his funeral bier, which could interact with Borusa and the assembled Doctors.

He granted Borusa his wish - but this was to turn him to living stone, imprisoned for all eternity on the bier.

During the Last Great Time War, the Time Lords resurrected Rassilon to lead them against the Daleks. This was in a younger incarnation, and he was as much a warrior as a scientist and politician. He armed himself with another of his artefacts - a death-dealing gauntlet - and wore armour under his robes.

With defeat on the horizon, he devised an elaborate plan. The Time Lords would ascend to a higher plane of existence, relinquishing their physical forms. Gallifrey remained locked within the Time War, so a bridgehead would be formed with Earth. Here were the last remaining Time Lords out with the time lock - the Doctor and the Master. A secret message was hidden within the Master's mind - a drumming sound composed of four notes, the heartbeat of a Time Lord. He would grow up with this sound in his head, and it would eventually drive him insane. On the last day of the war, just before the Daleks could destroy Gallifrey, Rassilon despatched a physical link to Earth - a gemstone from his staff which the Master would recognise as it was native to their planet. He could then use this to create the bridgehead that would draw Gallifrey out of the time lock and into normal Time / Space - putting the Earth at risk due to its proximity.

The Doctor was able to convince the Master that Rassilon's scheme would spell disaster - helped by the fact that the Lord President showed only arrogant contempt for the Time Lord who had just helped free Gallifrey. The Master fought Rassilon, and forced him back into the time lock, along with Gallifrey.

The planet was not destroyed, however. The combined TARDISes of twelve of the Doctors were able to save the planet by depositing it in a pocket of time at the end of the Universe. 

Rassilon continued to rule. He became obsessed by an ancient legend that stated that Gallifrey would be destroyed by something known only as "the Hybrid". He suspected that the Doctor knew what this was, and so entered into a bargain with the immortal Me to trap him. He would be imprisoned within his own Confession Dial - an object which Time Lords used to store their last will and testament.

After billions of years in a recurring nightmare world, the Doctor was finally able to break free and found himself on Gallifrey. He sought revenge more for the death of companion Clara Oswald - killed during the effort to ensnare him - than for his captivity.

Rassilon sent troops to capture him, but they remembered his actions during the Time War and refused to arrest him. The High Council were then sent to try diplomacy - but the Doctor rejected this. Eventually, Rassilon went to confront the Doctor personally, accompanied by a squad of troops who were ordered to kill him when he refused again to comply.

They rebelled, and Rassilon's power was broken. The Doctor forced him, and the rest of the High Council, into exile.

Played by Richard Mathews, Timothy Dalton, Donald Sumpter. 

Appearances: The Five Doctors (1983), The End of Time (2009/10), Hell Bent (2015).

• Rassilon is first mentioned in The Deadly Assassin, so is the creation of Robert Holmes - though he didn't appear on screen until the 20th Anniversary story, written by Terrance Dicks.
• In his novelisation of The Five Doctors, Dicks stated that Rassilon still lived, but on another plane of existence.
• Spin-off material has a triumvirate leading Gallifrey in its earliest days - Rassilon, Omega and "the Other", who may or may not be the Doctor, but probably is. Though never stated on screen, behind the scenes it was intended that the trio of Time Lords seen briefly in The Timeless Children are they.
• Richard Mathews was a character actor who appeared in the TV classic Children of the Stones and The Satanic Rites of Dracula in a career that spanned almost half a century (1948 - 1993).
• It had originally been hoped that Rassilon would be played by Charles Gray in The Five Doctors - Blofeld in Diamonds Are Forever and Mocata in The Devil Rides Out.
• Timothy Dalton will be best remembered as the fourth official James Bond, playing 007 in The Living Daylights and Licence to Kill. He was unavailable to reprise Rassilon in Hell Bent due to working in Dublin on Penny Dreadful.
• Donald Sumpter had previously played Enrico Casali in The Wheel in Space, and Submarine Commander Ridgeway in The Sea Devils. He also played the alchemist Erasmus Darkling in The Eternity Trap, one of The Sarah Jane Adventures.
• On audio, Rassilon has also been played by Don Warrington (Rise of the Cybermen and Death in Paradise), Terrance Hardiman (The Beast Below and The Demon Headmaster), and Richard Armitage (Robin Hood and The Hobbit trilogy).